After discussing a few things with my aunt, who is a doctor (but no RLS specialist), she brought up something that I also thought about on occasions: Do we know any connection between RLS and a hypersensitivity of the immune system?

There are a lot of things that make RLS behave similar to an allergy:

The age where most of us start to experience the symptoms, and the fact that there is a genetic disposition with an unknown trigger mechanism.

The way it can get more severe quickly for unknown reasons, and the fact that improvements are rare and usually a year long process.

The fact that there are so many different causes and remedies while the symptoms remain the same. Like, an allergy to some pollen may have essentially the same symptoms as an allergy to cats. Both may respond to the same medication (RLS: dopamine agonists and opioids), but have different causes.

This resonates with a conjecture I have, that augmentation includes a permanent acceleration of symptoms. There are so many cases where RLS is much worse (permanently) after a dopamine agonist therapy, even after the initial augmentation symptoms are over - very much like an allergy that will never return to mild symptoms after being aggravated for some time. (And I think that dopamine agonists should not be the first line of treatment, for this reason.)

I'm not saying RLS is an allergy, and of course these are only wild thoughts. But the mechanics of the symptom progress may be similar, there may be something in our body that over-regulates something which causes our symptoms, much like the immune system reacts to an allergenic agent. Is there any research in this direction?

Very interesting! No research that I know of, but others may know of something. I didn't even realize allergies could become permanently (or long-term) worse after a bout of aggravation. Sure is similar to augmentation. I agree, the dopamine meds should not be front-line, and a number of specialists are starting to make noise about it, too.